1. Field of the Invention
The present invention relates to filter assemblies.
One form of commonly used filter assembly comprises a plurality of elongate filter cartridges with each cartridge having an outlet end mounted on a plenum chamber, with the outlets communicating with the interior of the plenum chamber. In use, the whole assembly is inserted into a casing with the plenum chamber closing an open end of the casing. Liquid to be filtered is pumped into the casing, passes through the cartridges, through the outlets to the cartridges, into the plenum chamber and then exits the plenum chamber for onward processing.
2. Brief Review of the Prior Art
It has previously been customary to form the plenum chamber in two parts by an injection moulding process. Such a process is particularly suitable where a very substantial number of plenum chambers have to be produced, but is less cost effective when the number of plenum chambers to be produced is small.
The use of plenum chambers formed in two parts by injection moulding also has the disadvantage that a join must be made between the two parts and this introduces an extra manufacturing process. If the join is not sufficiently tight, leakage may occur.